Shane's World Right Arrow Reproduction Right Arrow Breeding the Medusa Pleco, Ancistrus ranunculus • Article © Geoff Haglund, uploaded November 01, 2012

It was a Friday (13 June 2012) and I was in full hunter gatherer mode. The pizza had been ordered (hunter) and I was just getting the beer from the fish room (gatherer), when I thought that I should have a quick check on the tanks before settling down for the night. In the corner of the Ancistrus ranunculus tank was a clutch of four yellow or gold coloured eggs. They were a warm colour like liquid honey and behind the closest rock was a clutch of another 5 eggs; but these were the more whitish eggs that I had seen in the past. I did a quick check of the cave to locate the male, as previously he had not thrown the eggs from the cave. There he was looking out at me and with a serious look on his face. Behind him was another female, she was facing into the cave. Lucky fellow I thought. Friday night, and two ladies hovering around.

I think it was also kind of lucky that eggs had been thrown from the cave, as the previous spawns on 20 March and 19 April had not gone too well with the male eating the eggs on about day 4 or 5. Typical male I thought, more interested in doing the business, than taking care of business. This time it was looking like he was going to have a clutch of eggs and so was I. The challenge was on. Me, a notorious failure with rescued egg raising versus mother nature and a lazy male.

I quickly took some measurements: Temperature = 27.2°C, pH = 6.28 TDS = 86. I transferred the eggs into a net and placed it so that the outlet from the HOB filter was partially flowing into the net, to keep the eggs moving. The next day I noted the male was in his usual odd position of facing out of the caves with the eggs high up under his body, effectively under his chin, and he was fanning appropriately. The eggs in the net were not doing so well. There was no sign of fungus but some of the eggs had “melted”. I concluded that the flow from the HOB was too strong and therefore the eggs had been pressed into the net with too much force and the egg shell had been broken.

I moved the eggs to generation one of the hatching tank. This is a small tank with gaps cut in the glass and fine mesh placed over the gaps, to allow water to pass from the main tank into the hatching tank. At this time I also changed the net from a medium grade net to a fine grade net, and placed an air stone under the net. The next day was another set of problems.

Eggs hatching

Eggs Hatching

Four days after hatching from egg

Four days after hatching from egg

19 days old

19 days old

33 day old - 2cm TL

33 day old - 2cm TL

Even though the tank water looked clean, it wasn’t! The fine grade of the net had a similar effect to the filter socks that some people use to catch fine particles of waste etc, before the outlet leads to a trickle filter. The result was that the fine net had gone brown with “dirt” and had become so blocked that the air stone was actually lifting the net, so that it was almost out of the water. The eggs were in grave danger of being lifted out of the water. I was never going to be able to keep the net clean enough, so I had to move to generation two of the hatching tank.

Generation two of the hatching tank, is the same as the generation one hatching tank except sponge is used instead of mesh in the gaps. Additionally I used an air lifter to pump water into the hatching tank from the main tank, and as the water left the hatching tank, via the sponge, the fine particles of dirt were trapped. There is also an air stone in this setup. It took 4 days for the eggs to hatch.

At this time the male had eaten, or otherwise disposed of his eggs. I have several theories relating to the male “loosing” his eggs (six or so times now). The first theory is that he was too new to the fatherhood business and as he kept the eggs so high up under his chin, when they started to hatch they irritated him, so he ate them. The second theory was that I was in fact disturbing him as I moved around the fish room, as the cave opening is actually at head height and so he was seeing my head move past all the time. The third theory is that there is in fact a second male in the tank, and he kills the fry by trying to enter the cave and fighting. The fourth and final theory, which came to mind when I saw a 10mm fry with egg sac moving around a stone, is that the male is actually ejecting the fry into the current as soon as they can move. This is not typical behaviour for an Ancistrus, but neither is this males position for fanning the eggs. The egg sac was fully consumed eight days after the fry hatched from the egg.

The specification of the breeding tank is a standard 2 foot tank: 24x12x12 (inches) and the best way to describe it is via pictures.

Tank 1

Spawning tank from above and

Tank 2

from above and to the side

The cave position can be seen in the second photo, at right angles to the filter flow. I sometimes find that when reading spawning articles I am looking for the “silver bullet” or magic recipe to making my fish spawn. There are too many parameters that need to be taken into account, and the magic bullet may not even be noted by the breeder, or just not documented. The pictures of the tank give all the information regarding the tank layout and position of cave. The cave is an “Easter island head” ornament - medium size). I have included below all the measurements taken from other spawning’s so that everyone has the best chance of breeding this wonderful fish. Ammonia = 0, Nitrite = 0, Nitrate = 5-10. Additional measurements recorded from other spawning’s (note that I did not record the dates for all spawning’s):

Date Temp pH TDS Air Pressure  
20th March 29.5°C (had been raised from 27.0°C) 7.1 134 1003.0hPa (there had been a 10hPa drop over the previous 48 hours)  
19th April Not Recorded - - 1032.8hPa (there had been a 5hPa increase over the previous 24 hours)  
13th June 27.2°C 6.28 86 1020.1hPa (there was no significant variation in the preceding days)  
11th October 27.9°C 5.48 128 1020.5hPa (there had been a 7hPa increase over the previous 24 hours)  


There is further information on this species on the Cat-eLog page.

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